Amino Acids

, 29:177

Almost all about citrulline in mammals

Authors

  • E. Curis
    • Laboratoire de Biomathématiques, E.A. 2498, Faculté de Pharmacie, Université René Descartes
  • I. Nicolis
    • Laboratoire de Biomathématiques, E.A. 2498, Faculté de Pharmacie, Université René Descartes
  • C. Moinard
    • Laboratoire de Biologie de la Nutrition, E.A. 2498, Faculté de Pharmacie, Université René Descartes
  • S. Osowska
    • Laboratoire de Biologie de la Nutrition, E.A. 2498, Faculté de Pharmacie, Université René Descartes
  • N. Zerrouk
    • Laboratoire de Pharmacotechnie, E.A. 2498, Faculté de Pharmacie, Université René Descartes
  • S. Bénazeth
    • Laboratoire de Biomathématiques, E.A. 2498, Faculté de Pharmacie, Université René Descartes
  • L. Cynober
    • Laboratoire de Biologie de la Nutrition, E.A. 2498, Faculté de Pharmacie, Université René Descartes
    • Laboratoire de Biochimie, Hôtel-Dieu, Assistance Publique – Hôpitaux de Paris
Review Article

DOI: 10.1007/s00726-005-0235-4

Cite this article as:
Curis, E., Nicolis, I., Moinard, C. et al. Amino Acids (2005) 29: 177. doi:10.1007/s00726-005-0235-4

Summary.

Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three “orthogonal” metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis.

Keywords: Citrulline metabolism – Urea cycle – Citrullinated proteins – Nitric oxide metabolism – Argininosuccinate synthetase – Ornithine carbamoyltransferase

Copyright information

© Springer-Verlag/Wien 2005